The RNA pseudoknot is an essential folding motif found in many classes of ribonucleic acids. Pseudoknot structures are involved in translational frameshifting, and they are found in the catalytic RNA component of RnaseP, and the cleavage site of the Hepatitis Delta Virus. Furthermore and in particular, recent evidence shows that pseudoknots are potent inhibitors of the reverse transcriptase of HIV, the virus that causes AIDS. To date, no crystal structure is available to elucidate the detailed molecular geometry and tertiary interactions of the pseudoknot. We were able to produce highly ordered single crystals of an RNA pseudoknot from Beet Western Yellow virus. We have crystallized a bromo-uridine single site derivative and plan on using MAD data collection to solve this structure.